Cooling system for indicator



Nov. 9, 1965 G. W. BORCHERS COOLING SYSTEM FOR INDICATOR Filed Feb. 15.1962 IN VEN TOR.

United States Patent 3,216,244 COOLING SYSTEM FOR INDICATOR George W.Borchers, Houston, Tex., assignor to Nordberg Manufacturing Company,Milwaukee, Wis., a corporation of Wisconsin Filed Feb. 15, 1962, Ser.No. 173,588 9 Claims. (Cl. 73-115) This invention relates to a systemfor preventing combustion or hot spot development in engine indicators,particularly, engine indicators adapted for measuring pressures inengine cylinders of the spark fired, compressed gas type.

An object of this invention is to provide a purging and cooling systemfor the hot spot which develops in engine indicators.

Another object of this invention is to provide a system and apparatuswhich efliciently prevents pre-ignition of the combustion chamber in aninternal combustion engine.

Still another object of this invention is to provide a simple andeconomical purging and cooling system which operates in cycles with theinternal conbustion engine.

Still another object of this invention is to provide a purging systemfor an engine indicator which intermittently operates so it does notinterfere or hamper the normal operation of the engine indicator.

A further object of this invention is to provide a purging system withmeans to intermittently stop its operation by automatic means when theengine indicator is recording pressure within the engine cylinder.

Another object of this invention is to provide a purging apparatus andsystem which utilizes compressed air as a medium for cooling the hotspot and other portions of the engine indicator.

The foregoing objects and other objects which will become apparent fromtime to time are now realized by the following invention which will bedescribed in detail and which is illustrated in the accompanying drawingof a more or less diagrammatic side elevation view of an engineindicator fitted on the cylinder head of an internal combustion engine.

The drawing shows a portion of a cylinder head generally designated as10 and a portion of the compression chamber 12 within the cylinder. Theengine indicator is generally designated as 20 and includes an engineconduit adapted to fit a cylinder head and communicate with the interiorof the cylinder, a housing 30 having within its bore a piston responsiveto the pressure within the chamber of the engine cylinder, a rod 35extending from the piston out of the housing, a calibrated spring 36providing tension against movement of the rod, a marking stylus 37 andan oscillating drum 45 to record pressure responsive movements of thepiston and rod in the housing of the indicator. Also shown is a cutoffvalve 14 placed in the engine conduit to open and close the passagewayof the engine conduit 10 between the engine cylinder and the engineindicator. The recording drum 45 may rotate at a constant speed or maybe adapted to oscillate and record the volume Within the internalcombustion engine by suitable connections to the crankshaft of theinternal combustion engine. Such connections are not shown in detail butare joined to a pulley 46 and to a pulley ring or equivalent means 47placed at the base of the recording drum 45.

The cooling system and apparatus illustrated herein include a source ofsupply of purging fluid (not shown), a supply conduit 50 carrying thefluid from its source and joined by a coupling nut 51 to a communicatingconduit 52 which empties into the interior of the housing 30. Thecommunicating conduit 52 has a check valve 55 located somewhere alongits length to provide unidirectional flow of the purging fluid or a flowthat is throttled from a high pressure supply of purging fluid into thehousing 30, but is not permitted to flow in a reverse direction.

The purging fluid is shown in the drawing to be admitted directly intothe housing 30 from where it moves into the engine conduit 15 to purgeor drive the combustible gases towards the engine cylinder and therebyprevent a hot spot developing generally in that portion of the engineconduit which is close to the engine cylinder. The purging fluid has acooling elfect on the hot spot which also helps to prevents undesirablepre-ignition or combustion, and allows the engine indicator toefliciently record the pressure within the engine cylinder.

The purging system which I will describe in greater detail is useful forengine indicators which measure generally all types of internalcombustion engines, but which has particular usefulness in thegas-fired, compressed gas type of internal combustion engine. The hotspot develops rapidly in the engine conduit of an indicator attached toa cylinder in this type of internal combustion engine. The rapiddevelopment of the hot spot and the increased likelihood of pre-ignitionfrustrates attempts to measure the pressure within the engine cylinderand may actually damage the engine indicator. The engine indicator,which has been generally described, has other working units and detailedmechanisms which drive and operate such units, but the foregoing are notessential to the practice of the present invention and will be referredto only by reference without detailed explanation or definition.

The source of the purging fluid may be any reservoir, compressionchamber or container which stores or maintains such fluid underpressure. The purging and cooling fluid is fed from such a supply intothe supply conduit and thereafter into the housing conduit whichcommunicates with the interior of the housing 30. A useful and eflicientpurging fluid is compressed air and it can be stored in standardcylinders or can be developed by conventional vacuum mechanisms. Anygases may, of course, be used to purge, buffer or drive away thecombustible gases but compressed air is economical and widely available.The fluid or the compressed air is desirably introduced into the housingat a sufficiently high pressure so that it quickly enters and scavenges,purges or drives away the hot gases in the interior of the hous ing andthe engine conduit 15. In general, the higher the pressure of thecompressed air, the more efiicient will be the purging and consequentcooling effect on the hot spot and other areas in the engine indicator.

The compressed air is admitted into the housing only during a periodwhich will be referred to as the purging cycle. During this purgingcycle, the admitted compressed air does not interfere with the pressureresponsive operation of the cylinder within the housing because thepressure in the engine cylinder is at its low point, which coincidesgenerally with the suction stroke and the exhaust stroke of the enginecylinder. During the compression stroke in the engine cylinder, thepressure builds up, and this pressure must be recorded by the engineindicator without interference from the purging fluid admitted into theengine indicator. Such accurate recording is made possible by placing acheck valve 55 or equivalent means in the housing conduit toautomatically close off or block the purging fluid during such pressurebuild-up, which shall be referred to herein as the recording cycle. Thecheck valve 55 may be\of the spring ball type or the trap door type orany equivalent type, which is designed to automatically close at aparticular pressure which is reverse to the flow of the purging fluid.Thus, the unidirectional check valve will allow the purging fluid orcompressed air to enter the housing at pressures, say of 250 pounds persquare inch during the purg- .which are jacketed by cooling means.

ing cycle, and the compressed air will be freely admitted into thehousing and the associated engine conduit. In the recording cycle, thepressure will increase until it exceeds a pressure of 250 pounds persquare inch. At such a time the calibrated check valve will close andblock any further passage of compressed air from the supvply source andthe supply conduit. The piston within the housing will be free toaccurately measure the pressure within the engine cylinder withouthaving its operaplified along the recording stylus onto recording cardsattached to the recording drum. Such recordings will, of

course, sketch a pressure curve that is meaningful in terms of acceptedpressure units. It is understood that the magnitude of the purging airpressure will be limited .by the compression and firing pressures in theengine .cylinder.

The purging pressure should not unduly dilute the air-fuel mixture inthe combustion chamber. Purging pressures as low as 175 p.s.i. have beenfound effective on indicators attached to engines having a compressionof 560 psi.

If desired, the action of the purging air may be supplemented byexternal cooling means such as a jacket of circulating water fixed tothe housing. Also, the purging gas may be routed to externally placedtubes Ordinarily, there is no need for such external cooling because thepurging gas may be properly set and controlled to efiectively reduce thehot spot. Adapters may be designed to fit existing indicators and suchadapters may have entry ports and fittings to receive a communicatingconduit from a pressurized supply of purging gas. Such adapters may beformed as a threaded annulus with appropriate ports and fittings. Otherforms and modifications are possible. While the purging gas has beendescribed as introduced into the housing holding the recording piston,this is not necessarily the only point of entry. The purging gas may beintroduced into the indicator at other points either directly or byusing an appropriate adapter and such purging gas need only be directedto the passageway in the engine conduit intermittently so it can flowagainst the 'hot air-gas combustible mixture from the engine cylinder.

The use and operation of my invention are as follows:

My invention allows an engine indicator to accurately record pressuresdeveloped within internal combustion engines, such as th spark fired,compressed gas type. The engine indicator is attached in communicatingrelationship with the interior of the engine cylinder, a zero pressurebase line is traced on the recording and, the

purging gas is introduced and the communication between the engincylinder and the pressure responsive piston in the housing of theindicator is completed by opening a cut-out valve 14. The pressure ofengine compression is recorded in the usual manner. The hot spot whichdevelops in the engine conduit of the engine indicator is prevented orkept at below pre-ignition levels by the purging system and apparatus.

During the recording cycle, the pressures in the engine cylinder areincreased and such increased pressures automatically close the checkvalve in the communicating conduit 55 so as to effectively block anycompressed air or other purging gas from a pressurized supply. Suchaction prevents any externally introduced purging fluid frominterrupting or interfering with the pressure responsive operation ofthe pistion within the housing. The piston now freely and accuratelyrecords the pressure from the engine cylinder and the movement of therod accordingly translates such displacement into acceptable pressureunits on the recording rod.

During the suction and exhaust strokes in the engine cylinder, thepressures within the indicator are reduced to levels lower than thepressure of the purging gas from the external pressurized supply. Thisopens the check valve and allows the purging gas to be admitted into thehousing during the purging cycle. Since the engine cylinder is at itslow pressure levels during the purging cycles, there is no interruptionof the recording procedure of the engine indicator. Such alternaterecording and purging cycles are continued as long as desired. Theintermittent flow of purging gas is directed against entry of the hotcombustible gases into the engine conduit. If the characteristics of aparticular internal combustion engine result in a high heat developmentdespite the purging system, then external means may be used to cool thepurging gas. In other Words, the intermittent purging cycle may besupplemented by externally cooled means.

The foregoing invention can now be practiced by those skilled in theart. Such skilledpersons will know that the invention is not necessarilyrestricted to the particular embodiments presented therein. The scope ofthe invenmovement of the rod, said spring calibrated to translate rodmovement in terms of pressure units and means to record such pressuresin terms of units, a supply of purging fluid, means to admit the purgingfluid into the --engine indicator at pressures less than recordingengine pressures, and means to stop the flow of purging fluid atpressures more than recording engine pressures, whereby said purgingfluid does not interfere with the pressure responsive operation of thepiston in the engine indicator.

2. The device of claim 1 further characterized in that the supply ofpurging fluid is admitted into the engine indicator generally at thehousing of said indicator,

3. The device of claim 1 further characterized in that the means toadmit the purging fluid into the housing consist of a closed conduit.

, 4. The device of claim 3 further characterized in that the means tostop the flow of purging fluid comprises a unidirectional check valve inthe conduit.

5. In an engine indicator having an engine conduit joined to a pistoncylinder of an internal combustion engine on one end and joined on theother end to a housing containing a closely fitting piston, a rodextending from said piston, a spring providing tension against movementof the rod, said spring calibrated to translate rod movement in terms ofpressure units and means to record such pressures in terms of units, asupply of pressurized purging gas, a conduit connecting said supply onone end and communicating with the interior of the housing 'at the otherend, means in said conduit to permit a unidirectional flow of thepurging gas from the supply to the housing, said means permitting theflow of purging gas at periods which generally correspond to the exhaustthe supply of purging gas is compressed air.

7. The device of claim 5 further characterized in that the supply ofpurging gas is compressed air and the means to permit unidirectionalflow is a check valve in the conduit.

8. In an engine indicator having an engine conduit joined to a pistoncylinder of an internal combustion engine on one end and joined on theother end to a housing containing a closely fitting piston, a rodextending from said piston, a spring providing tension against movementof the rod, said spring calibrated to translate rod movement in terms ofpressure units and means to record such pressures in terms of units, asupply of compressed air, a conduit connecting the supply of compressedair and the interior of the housing, a check valve disposed in theconduit, said check valve permitting a flow of compressed air into thehousing during periods which generally correspond to the exhaust andintake strokes of the engine, and said check valve stopping the flow ofcompressed air into the housing when the pressure from the enginecylinder exceeds the pressure of the compressed air flowing in theconduit, whereby said compressed air does not interfere with thepressure responsive operation of the piston in the engine indicator.

9. A method for cooling an engine indicator which communicates with theengine cylinder, said indicator having pressure responsive means andpressure recording means associated therewith, which includes the stepsof cycling purging fluid by delivering purging fluid into the indicatorat pressure levels to purge engine gases, in troducing said purgingfluid into the indicator at low engine cylinder pressures substantiallyoccurring at cylinder intake and cylinder exhaust, automaticallystopping the purging fluid when the engine cylinder pressure becomesgreater than a predetermined pressure of the introduced purging fluid,said increased pressure occurring at cylinder compression, and recordingthe engine pressure during such compression.

References Cited by the Examiner UNITED STATES PATENTS 2,595,425 5/52Thomson et al 73115 2,679,753 6/54 Flamm 731l5 2,741,128 4/56 Gadd et al73398 RICHARD C. QUEISSER, Primary Examiner.

1. IN AN ENGINE INDICATOR HAVING AN ENGINE CONDUIT JOINED TO A PISTONCYLINDER OF AN INTERNAL COMBUSTION ENGINE ON ONE END AND JOINED ON THEOTHER END TO A HOUSING CONTAINING A CLOSELY FITTING PISTON, A RODEXTENDING FROM SAID PISTON, A SPRING PROVIDING TENSION AGAINST MOVEMENTOF THE ROD, SAID SPRING CALIBRATED TO TRANSLATE ROD MOVEMENT IN TERMS OFPRESSURE UNITS AND MEANS TO RECORD SUCH PRESSURES IN TERMS OF UNITS, ASUPPLY OF PURGING FLUID, MEANS TO ADMIT THE PURGING FLUID INTO THEENGINE INDICATOR AT PRESSURES LESS THAN RECORDING ENGINE PRESSURES, ANDMEANS TO STOP THE FLOW OF PURGING FLUID AT PRESSURES MORE THAN RECORDINGENGINE PRESSURES, WHEREBY SAID PURGING FLUID DOES NOT INTERFERE WITH THEPRESSURE RESPONSIVE OPERATION OF THE PISTON IN THE ENGINE INDICATOR.